html,
body {
    display: flex;
    flex-direction: column;
    height: 100%;
    margin: 0;
}

nav {
    flex-basis: 60px;
    background-color: blueviolet;
}

article {
    display: flex;
    flex-grow: 1;
    justify-content: space-between;
}

aside {
    flex-basis: 300px;
    background-color: aquamarine;
}

section {
    flex-grow: 1;
    background-color: darkgray;
}

footer {
    flex-basis: 300px;
    background-color: black;
    color: white;
}